Viscous liquids, such as liquid soap, hand lotion, sun screen, shampoo, hair conditioner, or food condiments like mustard, catchup, mayonnaise, etc., pose particular difficulties in dispensing. The viscosity of these liquids makes it difficult to dispense them from standard, top-opening containers because the liquid tends stay in the bottom of the container even when the container is inverted. It often takes considerable patience on the part of the user to wait until the viscous liquid reaches the opening or the dispensing spout on the top of the container after the container is inverted. If the container is only partially full or if the liquid is particularly viscous, the weight of the liquid by itself is sometimes not enough to create sufficient shear force to overcome the viscosity and to initiate flow. The user must frequently resort to shaking or banging the container to coax the liquid out. It would be much more convenient for the user if the liquid were always close to the opening or dispensing tube of the container so that it is immediately ready to be dispensed.
One attempted solution to this problem that has been available for years is the use of pump-type dispensers on containers for viscous liquids. The dispenser pump typically has a scavenging tube which reaches down to the bottom of the container. Once the pump is primed with the liquid, it generally stays primed so that the liquid can immediately be dispensed by pressing on the pump without waiting for the liquid to rise from the bottom of the container. This, however, is an incomplete solution to the problem. Pump-type dispensers are rarely effective at dispensing all of the liquid which is inside the container, especially when the liquid is viscous. Some liquid nearly always remains in the bottom of the container beyond the reach of the scavenging tube. This is wasteful and it is frequently frustrating to the user who struggles to get the last bit of product out of the container. Particularly with viscous liquids, the dispenser pumps are also prone to dripping between uses which causes some small mess on the counter or shelf or on the outside of the container. Another problem with this solution is that the long, thin tubes that lead to and from the pump mechanism have a tendency to clog when the liquid dries or thickens in the tubes between uses. The complexity of dispensing pumps also makes them prone to breakage or mechanical failure and also adds to the expense of the container. Pump dispersers of this type are convenient for stationary, countertop use, but they pose special problems when traveling because the pump mechanism can be inadvertently activated inside of the user's luggage or purse when something presses against the pump when closing the luggage or when things move around inside the luggage during travel or baggage handling. Adding a locking mechanism or overcap to the pump dispenser for storage or travel solves this problem, but it increases the complexity and cost of the container.
Another solution to the problems associated with dispensing viscous liquids which has gained recent popularity in the packaging industry is the use of self-standing tube containers. Typically, a self-standing tube container consists of a flexible plastic squeeze tube or bottle with a screw-on cap that is adapted to act as a base to stand the tube on its end. The cap may be a simple screw-on lid or it may have a flip-top or a dispensing tube or spout incorporated into the cap. The cap is made with a wide, flat end surface that provides a stable base for standing the tube or bottle up on its end. Because the closed end of a squeeze tube is pointed, the cap is generally the only surface of the container suitable for standing the tube on a shelf, insuring that the container will always be stored in the correct inverted position. Likewise, when the container is a flexible plastic bottle, the end of the bottle opposite the cap is sometimes made with a rounded end so that the cap is the only surface suitable to stand the bottle on a shelf. Because the container rests on the shelf in an inverted position with the cap down, the liquid inside always settles near the opening or dispensing tube of the container for immediate dispensing. However, this too is an incomplete solution to the problem. Simple screw-on caps are inconvenient in this application, because it often requires three hands to operate them. If a user has picked up a container of, say, hand lotion with one hand and taken the cap off with the other hand, the user must put the cap down in order to dispense the hand lotion onto the free hand. Now the user has the container in one hand and a dollop of hand lotion in the other. He or she does not have a free hand left to pick the cap up and put it back on the container. However, he or she cannot set the tube down to finish applying the hand lotion because the only standing surface on the container is on the cap which is currently lying by itself on the countertop. This frustrating situation usually results in odd contortions or careful juggling acts to apply the lotion or to finagle the cap back onto the container without a free hand. Flip-top caps or caps with built-in dispensing tubes simplify this problem because the cap remains attached to the container during dispensing, but it is still difficult to close the container without a free hand so that it can be set down while applying the dispensed lotion. It would be desirable therefore to provide a container which does not require a spare hand and can close itself after the user is through with dispensing.